Not a race to fine Rio Tinto, senator told

The Australian corporate watchdog has been asked why it was slow to prosecute global mining giant Rio Tinto over a coal mining project in Mozambique.

Already, Britain has fined Rio Tinto STG27 million ($A47 million) for failing to write-down the failed investment and the US has launched legal action for fraud.

Greens senator Peter Whish-Wilson was questioning the Australian Securities and Investments Commission head at a hearing in Canberra about why it wasn't first, given Rio Tinto was company with dual listings in London and Australia.

"Senator, I'm not sure it's a race," commissioner John Price told the hearing on Thursday.

An investigation was underway in Australia and ASIC had been acknowledged by international counterparts for its assistance in their regulatory outcomes.

Mr Price said it was a complex investigation with 90,000 documents collected so far.

The committee hearing was told Britain's Financial Conduct Authority had used its administrative power to fine Rio Tinto, while the equivalent action by ASIC would be just $100,000.